Rotatable seal for cowlings



Sept. 30, "I95 M. E. CUSHMAN ROTATABLE SEAL FOR COWLINGS 7 Filed @511. so, 1951 2 SHEETS-SHEET l I 3mntor MAURKIE CU SHMAN Sept. 30, 1952 M. E. CU-SHMAN 2,612,227

- :RQTATABLE SEAL FOR COWLINGS Filed Jan. :50, 1951 '2 SHEETSSHEET 3 3nventor umce ECUSHMAN Patented Sept. 30, 1952 ROTATABLE SEAL FOR COWLINGS Maurice E. Cushman, ;Verona, N. 3., assignor to Curtiss-Wright Corporation, a corporation of Delaware ApplicationJanuary-EIO, 1951, Serial No. 208,636

8 Claims.

This invention relates to spinners for aeronautical propellers and more particularly to a sealing arrangement for controllable pitch propeller blades where they pass through a propeller spinner. The invention, in part, comprises improvements over .that described and claimed-in Patent No. 2,522,083, issued September 12, 1950, to Leo Avondoglio.

Sheet metal spinners have .been used for some time tosurround .a propeller hub and to embrace the propeller blades, so that airflow over the .outside of. the spinner is streamlinedfor minimum drag of the propeller. In modern high speed aircraft; this spinner streamlining becomes particularly important for drag reduction'butthe problem of adequately sealing the bladesas they pass through the spinner becomes troublesome particularly where the propeller blades have considerable chord and where the spinner diameter .is .relatively small. For .instance,'if a spinner has a diameter of the order of 2 feet and the blades of a three-bladed propeller each have a chord of about'l l inches, the openings in the spinner through which-the blades passhave large size relative to the spinner. If bumps onrthe spinner are. used, with the blades .starting beyond the profile of the spinner, increase in drag is immediately caused.

, If an arrangement such as in the Avondoglio patent above mentioned is used, the warping blade seal is difiicult'to control and .retain due to the considerable curvature thereof resulting from the small spinner diameter.

This invention sets out to providela warpingblade seal for a small diameter spinner whose position and shape is at all times perfectly controlled to the end that the spinner seal conforms to the profile of the spinner andto the end that minimum dragzis induced in the system;

It .is .an object of the present invention to provide an efiicient, low drag, fully controlled spinner seal for the blades of a controllable pitch propeller. It is a further object of the invention to provide -a propeller and hub construction of relatively small diameter, whichincludes provision for affording sealing of 1 the blades as'they pass througha rotating spinner associated with the propeller. A further and principal object of the invention is to provide reinforcing .means for a rotatable spinner seal to support the seal against centrifugal force during propeller rotation. It is a further object of the inventionto-provide-a multi-part spinner andstreamlining for-a propeller wherein a central portion of the spinner is secured to and rotates with the propeller, said central portion being bordered by non-rotating forward and rearward parts. In this connection, the nonpropeller system. Furthermore, with a, non-' rotating spinner entry, the non-rotating portion maytcontain various sorts of auxiliary apparatus which .add to the utility of the aircraft on which the installation is made.

Further objects of the invention will become apparent .inJreading the annexed detailed de scription in .connection with the drawings which exemplify. .a preferred arrangement of the spinner and associated parts. The drawings and description are not to be considered as limiting the scope .of the invention, the specific improvements which comprise the invention being set forth in the appended claims.

In the drawings, in which similar reference characters indicate similar parts,

Fig. 1- is a fragmentary longitudinal view, partly in section, through an aircraft propeller and spinner showing the provisions of the in-' vention.

Figs; 2 and 3 are fragmentary elevations of the propeller and spinner assembly, showing one of the'propeller'blades in different positions of p d I v Fig. 4 is a fragmentary longitudinal section through a portion of the propeller showing details of construction thereof; and

Fig. {5 is'a frontal view, partly in section, of the spinner and propeller hub, also showing certain details'of construction of the invention.

In the figures, "a propeller shaft is indicated at H], the shaft extending forwardly from a nose'structurell of the aircraft. Upon the shaft [0 a propeller hub 12 is mounted through splines l3 and conventionalsecuring means I 4,

the propeller hub including blade sockets, one

of which is-shown at l-5. Upon a rearward extension IB of the propeller hub, a pitch changing mechanismil is mounted, the mechanism 11 being piloted on the propeller hub so that the .hub -may rotate relative thereto. -The mechanism'is secured against rotationto the structure II by suitable dowel arrangements l8. The mechanism I! may be provided at its rim with lugs 19 to whichbraces 20 are secured as at 2|,

ithe braces l ll providing a forward mounting and anchorage for a rearward stationary cowling 22.

Embracing the propeller hub I2 is a rotating spinner cowling 23, attached to the propeller hub |2 by a forward diaphragm 24 and a rearward diaphragm 25, the two diaphragms being secured to the front and rear portions of the rpropeller hub as by screws 26 and 21. The spinner 23 may be made inseve-r-al segments, as shown in Fig. 5, these segments being secured to each other at flanges 29, whereby spinner construction may be accomplished by the use of stampings rather than by the use of a spun conical mem bet. The spinner 23 is conical in form, at least in its central portion, and circular openings are provided there'around through which propeller blades 3| project, the openings having a diameter somewhat greater than the chord of the blades. The blades 3| in the embodiment shown are sub stantially rectangular in planform in their airfoil portions and these airfoil portions extend within the spinner 23 and terminate in a circular shank portion 32 secured within the hub socket H). A transition from the airfoil portion 3| of the blade to the cylindrical portion 32 thereof is accomplished by a blending shank portion 33 shown in Fig. 5. They inner end of the shank 32' is provided with a flange 34 engaged by an inner bearing race 35 engaged in turn by hearing balls 36 engaged in turn with a bearing retaining nut 31 screwed within each hub socket |5.-' By this arrangement, each propeller blade is secured within its hub socket and is capable of rotation about the blade axis for pitch change. Pitch change is imparted to the propeller blades through the engagement of a hub-carried worm seengaging a worm wheel 40 secured to each blade flange 34. Driving connections to the worms 39 are effected from the pitch change mechanism l1, these connections not being shown since they have been adequately disclosed in the prior art and do not .comprrise a portion of the invention. A pitch changing arrangement for a propeller of this type is exemplified by Mergen et al. patent application S. N. 143,636, filed February 11, 1950. r I

As previously indicated the spinner 23 is provided with-substantiallycircular openings, designated at 42, through which the propeller blades 3| pass. These openings are circular whenthe spinner cowl 23 is fiat; when the spinner cowl 23 is curved to conical form, the openings 42 depart in their projected form from a true circle, but remain effective as circles on the surface of the spinner cowl. As will .be noted bythe proportions of the drawings, these openings are rather large and if they are not sealed in some manner, the smooth continuity of airflow over the exterior of the spinnerwould be seriously interfered with. These openingsneed to be substantially circular since the propeller blades have a pitch change range ofapproximately 120 degrees from a feathering position as shown in Figs. 1 and 3-5, to a negative pitch angle of about degrees. The border of each opening 42 is constructed With a track comprised by the spinner material at the edge of the opening as at 43, and an annular element 44 underlying the edge 43 in spaced relation and secured as'at 45 to the spinner 23.

A flexible circular seal disk 46 is provided with a slot 4! having clearance relation with .the propeller blade 3| and embracing the blade. A seal gasket 48, fitted to the disk, cushions and seals the joint between the blade 3| and the sealing disk46. The disk 46 is elastically curved to a conic configuration to conform to the profile of the spinner 23, the edges of the disk 46 being engaged in the track formed by the elements 43 and 44. As the propeller blade is rotated for pitch change, the disk 46 rotates therewith but because of the flexibility of the disk, it may curve along different diameters thereof as the disk is rotated so that the outer surface of the disk at all times conforms to the general-conic shape of the spinner. The several views of the drawings are believed to show this arrangement, Figs. 2 and 3 particularly indicating two pitch positions of the propeller blades while the spinner'seal45 remains in the curvature of the spinner 2-3. The shaded lines in these two figures may be con sidered to represent surface elements of the section of the spinner and of the spinner seat disk 46, these surface elements remaining the same regardless of the pitch position of the propeller blades and of the degree of turning of the spinner seal disk 46 in the spinner.

With the propeller rotating at high speed, the seal disks 46 are disposed in a high centrifugal field which, if not compensated, would tend to buckle the disks and to fling them outwardly so that they might either be thrown from the propeller or might buckle to the point where they would jam in the spinner tracks and not be capable of free rotation with the blades as the blades change in pitch. To reinforce the spinner disks 46 against the effects of centrifugal force,

a plurality of struts 50 are secured to the disk as shown in Figs. 1 and 5, there being a total of 8' struts for each disk in the arrangement shown.- Inner struts 5| are pivoted to the struts 50 at-52, the struts 5| at their inner ends carrying yokes 53 engaging around a cam track 54 formed on an inner tapered bore on the blade retaining nut r 31 screwed into the blade socket 5. The cam track 54 is of annular waved form as indicated in Fig. 4, the rise and fallof the cam parallel to c the blade axis being a function of the rise and fall of the edge of the opening 42 in the spinner parallel to the blade axis. The several struts 50, 5|, accordingly, secure the disk 46 in a conic configuration the same as the conic configuration of the spinner 23. The yokes 53 carry rollers 55 engaging the underside of the cam track 54 so that, when the propeller is rotating, the struts and yokes may travel freely around the cam track as the propellerblade is changed in pitch. The yokes 53 are driven with the propeller blade during pitch'change of the latter so that the yokes will at all times engage the proper portion of thecam track to hold the spinner disk in its correct; position, and also to drive the spinner disk .46, with the blade when vblade pitch is changed.

This drive avoids direct driving of the disk by the blade through the possible buckling of the seal disk. To this end, the shank 33 of the blade is provided with lugs 57 to which spiders 58 are secured. The spiders are provided with grooves 59 within. each of which a yoke 53 is engaged. To stabilize the drive ing of the disk, each strut 5| is provided with an extension 56, slidablyengaging a corresponding groove 59 in the spider 58.

sions 56 are constrained to turn therewith, sliding up and down the grooves 59 in accordance with the configuration of the waved cam 54, and driving the disk 46 through the struts 50 and 5|.

Part of the centrifugal load on the disk 46 is carried by the struts 50, 5| while part of it is also carried where the edge of the disk 46 engages the gasket seal 48, avoiding Thus, as the blade. turns for pitch change, the yokes 53 and extentrackelements43 and 44. At the diskfedge, low friction'gaskets, preferably of phenolic compositlon, are secured on either side of the edge of the disk-46 50 that as the disk turns-in: the. track, undue resistance will not be' encounteredas a result of the'centrifugal force acting on the disk.

As will be noted in the figures, thexinner ends of the edgesof" the airfoil portions of the 'proe peller blades are curvedasat 60 to accommodate the relative radial motion of the disk to the blade-3| as the blade is turned for pitch change. This arrangement enables the presentation :of airfoil sections of the propeller blade on the outer surfaces of the cowling at all times, to minimize the drag in the system. i v v In the form of spinner and propeller systems contemplated in this application, the nose portion of the spinner has a high fineness ratio, the nose portion of the spinner extending outwardly beyond the propeller a substantial distance to minimize drag in the system. To avoid balancing problems on a long slender spinner of this sort, the arrangements of this invention allowthe forward portion ofthe spinner to be mounted non-rotationally. To this end, a non-rotating sleeve 62, secured within the structure l l,'passs through the propeller shaft 10,: the shaft rotating around the sleeve. The forward end of the sleeve 62 is piloted with respect to the propeller, through a bearing 63. Brackets 64', secured to a fitting 65 at the forward end of the sleeve, support the nonrotating forward cowling 66 through fittings 61. In view of the hollow nature of the forward stationary cowling 66 and of the sleeve 62, various sorts of equipment such as instruments and the like may be incorporated in the forward cowling.

Various modifications may be made in the invention while still coming within the scope thereof. For instance, the cam track 54 and associated elements of the system need not necessarily be a portion of the propeller hub and blade retaining nut, but rather, such cam track could be secured to the propeller hub as a separate assembly. The number of struts 50, 51 with their associated elements may be increased or decreased to .provide adequate support for the spinner disk 46 in accordance with the Weight and dimensions of the part to be supported. The spider arrangement 58 is susceptible to considerable change and modification as the proportions and character of the propeller blade used in connection with the invention might vary. Suitable reinforcement-may be provided in the seal disk 46 at those portions thereof adjacent the leading and trailing edges of the propeller blades where the material doe-s not have as much body as in other portions of the spinner disk where greater surface area of material exists. Also, the spinner disk can be completely supported by the cam and strut arrangements above described without recourse to auxiliary support of the spinner disk edges by the rotating spinner.

Though but a single embodiment illustrating the invention has been illustrated and described, it is to be understood that the invention may be applied in various forms. Changes may be made in the arrangements shown without departing from the spirit or scope of the invention as will be apparent to those skilled in the art and reference should be made to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. In an aeronautical propeller and cowling arrangement, said propeller having blades extending through said cowling for pitch change, a

substantially circular trackin the cowling around each blade, a warpable substantially circular closure member embracing each blade in clearance relation and movable with said blades and fitted to said track, the latter lying in a conic surface and'said closure member'conforming to said conic-surface in all'pitch positions of the associated blade, a waved substantially annular cam concentric with .the blade and secured to said propeller, said cam-being waved substantially in conformance with the profile of said track, a plurality of 'struts engaging said cam and secured to the inner surface'of said closure mem benand means on the propeller blade engaging said struts to drive said-struts about the blade aXi-s'asthe-bla'de changes in pitch.

2. In a-rotatingcowling-for an aeronautical propeller comprising a controllable pitch blade, a conic'surfaceportion of said'cowling adjacent saidblade having a circular opening through which said blade passes, a closure disk embracing the blade inclearance relation and movabl'e with the blade'during pitch change, said disk being warpabl'eto the profile of said conicsurface, a

waved earn, secured to said propeller within said cowling; a; plurality of 'cam followers spaced aroundand' engagingsaid cam, means securing said cam {followers to said disk, and means to drive said means and disk rotationally about 'th'e 1 blade axis as said blade is changed in pitch.

3. In a rotating cowling for an aeronautical propeller comprising a controllable pitch blade, a conic surface portion of said cowling adjacent said blade having a circular opening through which said blade passes, a closure disk embracing the blade in clearance relation and movable withthe blade during pitch change, said disk being warpable to the profile of said conic surface, a waved cam secured to said propeller within said cowling, a plurality of cam followers spaced around and engaging said cam, means securing said cam followers to said disk, means to drive said means and disk rotationally about the blade axis as said blade is changed in pitch and track means secured to the cowling edge bordering said circular opening, the closure disk edge being engaged in said track means.

4. In a rotating cowling embracing a propeller, said cowling having a conic surface, said cowling having a substantially circular opening through which a blade of the propeller projects, said propeller including a hub and a blade socket, a waved cam secured to said socket having a wave configuration like the configuration of the edge of the cowling opening,.a plurality of cam followers movable around and engaging said cam, a strut secured to each cam follower, and a warpable closure disk embracing the propeller blade to the inner surface of which said struts are articulately secured in spaced relation.

5. In a rotating cowling embracing a propeller, said cowling having a conic surface, said cowling having a substantially circular opening through which a blade of the propeller projects, said propeller including a hub and a blade Socket. 9. waved cam secured to said socket having a wave configuration like the configuration of the edge of the cowling opening, a plurality of cam followers movable around and engaging said cam, a strut secured to each cam follower, a warpable closure disk embracing the propeller blade to the inner surface of which said struts are articulately secured in spaced relation, and means for driving said cam followers around said track with the propeller bladeas it changes in pitch.

6. In a rotating cowling embracing a propeller, said cowling having a conic surface, said cowling having a substantially circular opening through which a blade of the propeller projects, said propeller including a hub and a blade socket, a waved cam, secured to said socket having a wave configuration likethe configuration of the edge of the cowling opening, a plurality of cam followers movable around and engaging said cam, a strut secured to each cam follower, a warpable closure disk embracing the propeller blade to the inner surface of which said struts are articulately secured in spaced relation, and means providing interengagement between the edge of said disk with the cowling edge at said opening. I

7. In a controllable pitch propeller system comprising a hub and sockets, and blades rotatably secured in said sockets for pitch change, a blade retaining nut screwed into each socket and embracing the associated blade, said nut having clearance around said blade and having a waved cam track formed thereon, a warpable disc surrounding the blade outwardly of said hub socket, a plurality of cam followers spaced around said c'am' track, and a 'lurality of means securing said warpable disk said cam followers.

8. A propeller system including a hub having controllable pitch blades extending therefrom, a spinner secured to and rotatable with saidhub,

a curved guide carried by the hub within said spinner,.a streamlined air entry cowl in advance of and blended into the form of said spinner, means mounting said air entry, cowl against rotation with the propeller, said-spinnerportion having openings through which the blades of the propeller project, flexible means movable with the propeller blades as they turn for pitch change to seal the blades to the surface of said spinner, and mechanism articulately connecting said curved guide with said flexible means, to conform the shape of said flexible means, at all times, to the shape of said spinner.

MAURICE E. CUSHMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Date Number Name 2,494,368 Steele et al. Jan. 10, 1950 2,498,072 Dean Feb. 21, 1950 2,522,083 Avondoglio Sept. 12, 1950 FOREIGN PATENTS Number Country Date 571,989 Great Britain Sept..18, 1945 

